Mobile devices are often designed to work with multiple wireless networks. For example, a mobile device may be able to operate in a number of 2G and 3G cellular networks, such as GSM and GPRS, EDGE, CDMA, UMTS, and HSDPA, as well as with networks that use IEEE 802 wireless standards such as WiFi, WiMax, and Bluetooth. Additionally, the mobile device may allow seamless roaming between a local area network, such as WiFi, and a cellular network, such as GSM.
The number of wireless networks that a mobile device is able to operate within depends in part on the user's service provider. For example, one service provider may configure the mobile device to use the GSM wireless network standard for transmitting voice data to and from a cell site and the EDGE wireless network standard for transmitting data to and from a cell site. However, another service provider may instead use the CDMA wireless network standard for transmitting voice data to and from a cell site. Additionally, when Wi-Fi coverage is available, the mobile device may be configured to use a WiFi network to transmit data to and from a wireless router.
The mobile device typically has a separate radio for each wireless network it is able to operate within. Each of these radios is typically always powered on during operation of the mobile device since the mobile device could be within the coverage range of any one of the networks and therefore wish to communicate on any one of these networks. However, the power drain from powering multiple radios simultaneously can be considerable, and can be a concern, especially if battery power is at a premium.